The present invention relates to an electro-optical display containing an electrochromic material held in two electrode-carrying support plates to manifest reversible variations in the light absorption properties upon application of properly controlled voltage or current. This display is referred to as an "electrochromic display (ECD)" hereinafter.
The present invention relates, more particularly, to electrode structures connected to segment electrodes in an electrochromic display (ECD) of the segmented type.
It is well known that an ECD comprises a pair of substrates, at least one of which is transparent, a desired number of display electrodes formed on the transparent substrate, an electrochromic material film formed on the display electrodes, a counter electrode formed on at least one of the pair of substrates, and a liquid electrolyte disposed between the pair of substrates.
In such an ECD, it is preferable that an area of each of the display segments having the electrochromic material film thereon and a resistance value of a lead-in electrode connected to each of the display segments be provided such that their product was approximately constant, to provide stable visibility to some extent.
A conventional lead-in electrode resistance controlling technique was disclosed in Hiroshi Hamada et al, U.S. Pat. No. 4,153,344, issued May 8, 1979 and assigned the present assignee, entitled "LEAD-IN ELECTRODE STRUCTURE FOR ELECTROCHROMIC DISPLAYS OF THE SEGMENTED TYPE".
However, even if the product of the area of the display segment and the resistance value of the lead-in electrode connected to the display segment is unvaried, further disadvantages are likely to arise. That is, the resistance value between the lead-in electrode and certain points of the display electrode under the electrochromic material film in any one of the display segments will be different depending on the locations of these points of the display electrode, in particular, remarkably so as the area of one of the display segments is increased. Upon applying power (energy) to this particular segment, the degree of coloration over this display segment becomes disordered because the resistance values between the lead-in electrode and the points of the display electrode are changed. Therefore, stable visibility over all of the display segments can not be provided.
Therefore, it was desired that the resistance value between the lead-in electrode and every point of the display electrode under the electrochromic material film in any one of the display segments be uniform to provide for stable visibility over the display segments.